This invention relates to wick operated liquid fuel burning devices and in particular to an improved liquid fuel regulator and an improved wicking device.
Wick operated liquid or solid fuel burning devices have been used for centuries as a means of providing controlled burning of such fuel to give light or heat.
Candles and oil burning lamps are two familiar examples of such devices. Candles have an elongate textile wick extending through a solid wax shaft where the burning of the wick heats and melts the surrounding wax which supplies the combustible fuel to keep the wick alight.
Oil burning lamps are more complex devices where a wick is suspended in a reservoir of combustible fuel and the capillary action of the wick draws liquid fuel up the wick to supply the combustible fuel to the burning area of the wick.
The quality and quantity of flame achieved by wick operated burning devices is governed by a number of factors including the type of combustible fuel used, the capillary action of the wick which controls the quantity of fuel reaching the burning surface and the amount of wick exposed for burning which affects the quantity of oxygen available to support combustion.
The expected performance of wick operated burning devices varies with the nature of the device but generally limitations in performance are attributable to one or more of the above factors. For example, in conventional burners the height of the wick determines the size of the flame and the rate of fuel use. Therefore the burn time available is dependent on the height of the wick above the combustible fuel holding receptacle and the capacity of the reservoir holding the combustible fuel. However, it has been determined that for normal wicks, the practical maximum depth of combustible fuel that can be accessed is approximately 5 inches or 125 millimeters. This limitation is due to capillary flow limitations of the wick which limits the height fuel can be drawn up a wick For large diameter burners, such as 60 millimeters or larger, the liquid volume can be greater than 200 milliliters and provide a burn time of twenty hours or more providing the vertical height of the burner does not require a wick of more than 125 mm in length. However, such burners look bully and cumbersome and do not always provide an appropriate aesthetic appearance.
For example, burners may be used to imitate a candle. Candles have been used as a decorative and practical lighting means for many centuries. However, the wax residue and the deformation of shape when wax candles used do not contribute to their decorative features. As an alternative to wax candles it has been suggested to use a fuel-burning lamp emulating a candle shaped lamp. Such a fuel-burning lamp could comprise a reservoir holding combustible fuel, upon which tubular members extend in order to provide a candle shaped burner. A wick extends from an upper external part to the internal bottom of the reservoir base. The technology used to provide and operate such candle imitating lamps has, to date, simply followed the basic principles of conventional burner design. However, as previously described, such design has limitations, particularly for wick length such that elongate candle shaped lamps often exceed the maximum practical wick length of 125 mm. A further problem involves the burn time of such lamps. Lamps capable of long burns tend to be squat and are shaped differently to a slender and elegant candle shape.
However, when burning lamps are constructed in the shape of elongate candles their size only provides a burn time of about 3 to 4 hours. Many functions such as wedding receptions and the like may extend for a period of some 6 to 8 hours. Therefore these known liquid burners must be refueled and are often considered not appropriate and not used for such events.
Various attempts to address this problem have been considered. In one proposed solution a wick extends into a fuel reservoir having a particular capacity that is filled with combustible liquid and when that combustible liquid is finished an electric pump system pumps further fluid to refill the reservoir. In this way, an extended time period of candle burning can be achieved. However, such an apparatus requires a separate power supply with a control network to pulse the electricity when the reservoir needs replenishing.
Another significant problem with known oil lamp wick systems is the variation of the size of the flame dependent on the depth of oil in the reservoir. As can be determined by the maximum practical depth of the reservoir being 5 inches or 125 millimeters there is less capillary flow when the reservoir is nearly empty and the wick must draw the oil from near the bottom of the wick over a small surface area to when the reservoir is full and the wick is drawing oil from near the top of the reservoir over the whole length of the wick The size of the flame will also be dependent on wick diameter, wick protrusion, wick material, wick structure and the like with a combination of the above determining wick capillary action. The known oil burners can be set up to provide a reasonably pleasing effect. However, there is an inherent variation of wick capillary flow which depends on the distance that the oil must flow and the amount of wick exposed to the oil/fuel. In particular, a full reservoir provides the entire wick length and large surface area thereof with a high capillary drawing of fuel which gives rise to a rich fuel mixture. As the fuel level decreases in the reservoir the amount of fuel drawn by the wick decreases as less wick surface area is exposed to the fuel, and the fuel/oxygen ratio optimises. However, as the fuel level continues to drop, the wick surface area exposed to fuel also drops giving rise to a lean mixture. Accordingly, in most liquid fuel burners the fuel mixture supplied to the wick over the time period the fuel reserves are consumed is in a state of continuous flux leading to a constantly fluxing flame.
Furthermore, the wicks in such burners suffer premature deterioration due to the non-optimal burning.
All the above problems result in practical and aesthetic limitations to the use and potential application of liquid fuel burning devices whether used as lighting lamps or heating lamps.
In the case of lighting application where burners emulate wax candles, the limitations are particularly acute as any uneven burning over the burning range of lamp can be quite undesirable and the desirable shape of the lamp (long and thin) provides a very limited available fuel supply to such shaped lamps.
One way of overcoming such limitations is to start with a larger than required aesthetic size. However, a larger size of burner will still suffer from uneven burning albeit over a longer length of time. Moreover, such articles, if used on a number of tables at a restaurant over many nights, will substantially increase costs and render such a system unacceptable in many commercial enterprises. The currently available oil lamps do not satisfactorily address this problem or provide any viable solutions.
In the case of heating lamps the uneven flame is undesirable and the limited burn time is also a problem. In addition such lamps due to their compact heat retaining design may lead to undesirable heating of the fuel reservoir as the exposed wick is generally positioned in close proximity to the fuel reservoir.
It is an object of this invention to provide an improved wick operated liquid fuel burning device and an improved liquid fuel regulator.
Accordingly in one aspect the invention provides an improved liquid fuel burning device comprising a first reservoir adapted for holding a supply of said liquid fuel, a wick system adapted to co-operate with said first reservoir to draw fuel therefrom for combustion wherein said first reservoir has a fuel feed tube communicating between the interior and exterior of said first reservoir and wherein said first reservoir can be closed to form a substantially air-tight seal such that as fuel is consumed from said first reservoir a partial vacuum is created within said first reservoir which automatically draws further fuel up said feed tube from a second fuel reservoir and a constant fuel supply is maintained in said first reservoir.
The first reservoir may take the form of a small pod having a sealed bottom and an open top.
The wick system may comprise a wick tube which traverses a cap. The wick tube will be fitted with a replaceable wick adapted to snugly fit said wick tube and the cap may be provided with a seal such that the cap can cooperate with the open top of the pod to maintain a substantially air tight seal with the pod.
Alternatively the wick system can be supplied complete as a disposable unit.
The feed tube may have a first aperture and a second aperture wherein the first aperture is positioned within said pod toward the top thereof and the second aperture is positioned outside said pod.
The second fuel reservoir may take the form of an elongate tube and will most preferably have a shape similar to an elongate wax candle.
In another embodiment the invention provides a lighting device comprising one or a plurality of the aforesaid burning devices associated with one or more second fuel reservoirs.
In another embodiment the invention provides a heating device comprising one or a plurality of the aforesaid burning devices associated with one or more second fuel reservoirs.